Many of us have heard of large concrete block towers to store electricity. Kinetic energy is stored when the blocks are raised to the top of the tower, and released when they are lowered. This is the Energy Vault project, which we present here.
The technology proposed by Energy Vault
Energy Vault offers two types of product: long-term storage using concrete blocks and gravity energy, and more conventional products, short-term storage (apparently mainly battery-based) and a charge management software suite.
Long-term storage
This is the company’s main focus: long-term energy storage using concrete blocks. While the idea is appealing, I haven’t found an independent source to support its viability.
The Energy Vault concrete tower
Initially, Energy Vault made a name for itself with a project involving giant cranes to move concrete blocks upwards (to store energy) or downwards (to release it). In this way, they built immense towers. The company claimed an efficiency of 90% and could reach maximum power in 2.9s.(source) A 120-meter tower could store 20MWh. The cost would be between $280-350/kWh and could go down, according to Robert Piconi, head of the startup, to $150/kWh. (Combier 2018) In 2019, they announced a capacity of 35 MWh, a maximum output of 4 MW and an LCOS of $0.05/kWh compared with “$0.17 per kWh for STEPs”. (Colas des Francs 2019) The company was still announcing a LCOS of €0.042/kWh in 2021. I have not heard of any confirmation of this. These LCOS claims leave me rather suspicious.
This model has made the headlines, claiming great performance and being scalable in principle. Nevertheless, it has been widely criticized, not least for the risk of mechanical wear and tear and of being caught in the wind. A working prototype, 120m high and named “EV1”, was built in Switzerland’s Ticino region. This version appeared to be a success, with the company reportedly selling 3 projects totalling 1.6 GWh of storage for 520 million euros by 2021.
It clearly failed to convince, and the company moved on to another model.
The new model
Following Energy Vault’s IPO, another sustainable storage solution was designed, called the “Energy Vault Resiliency Center” (EVRC). This time, it takes the form of a large warehouse-type building, with the blocks stored on metal frames.
While this solves the problem of wind load, it raises the question of the quantity of resources required.
An agreement had been signed with Atlas Renewable for an installation in China. Construction of a 100MWh facility is due to start in March 2022. An agreement was signed in September for a 2GWh global installation.
Short-term energy storage and software
Energy Vault also markets “short duration energy storage” (SDES) systems (<4h), including lithium-ion batteries. 500MWh of this system has reportedly been purchased for the 330MW Meadow Creek solar park, near Melbourne (Australia).
The company also markets a charge management software suite.
A criticized technology
A report from a rather special organization (they do negative reports and bet on the stock going down, if I understand correctly) points out anomalies:“Energy Vault (NRGV): New Evidence Leads Us To Downgrade This Company To A Middle-School Science Fair Project“. Energy Vault responded in a press release.
The company’s communication leaves a bad impression. I couldn’t find anything to explain the decision to change the model. Above all, the claim of a system 3 times cheaper in LCOS than STEP makes me frown. What’s more, while the executive had announced several contracts in 2019, I didn’t see any echoes afterwards … Ditto in 2021 ..
Progress and news
Energy Vault is a spin-off from the stuatup studio Idealab. It was founded in 2017 in Switzerland. It had a first large investment round in May 2019, with Cemex and $110 million from Softbank Vision Fund. A second round of $100 million brings together Aramco Energy and the previous investors in August 2021.
In February 2022, the startup’s holding company is listed on the New York Stock Exchange. Sales in 2022 are estimated at between $142 and $152 million.
- Combier E., “Quand le béton fait office de batterie”, Les Echos, August 26, 2018
- Colas des Francs O., “Quand le mouvement sert à stocker l’energie”, Les Echos, October 23, 2019